Support for additional decoding processing time in wireless LAN systems

ABSTRACT

A wireless communication device in a wireless system may generate a High Efficiency Physical Layer Convergence Procedure (PLCP) Protocol Data Unit (HE PPDU) frame including (i) an Orthogonal Frequency Division Multiplexing (OFDM) symbol including padding bits and (ii) an extension having a non-zero signal strength, and transmit the HE PPDU frame. A High Efficiency signal (HE-SIG) field of the transmitted HE PPDU frame may include an indication for a duration of the extension to avoid ambiguity of the extension. A communication device in a wireless system may receive an HE PPDU frame including (i) an OFDM symbol including padding bits, and (ii) an extension having a non-zero signal strength, and transmit an Acknowledgement frame a predetermined inter-frame space after an end of the HE PPDU frame. An HE-SIG field of the received HE PPDU may include an indication for duration of the extension to avoid ambiguity of the extension.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/894,531, filed on Jun. 5, 2020, which is a continuation of U.S.patent application Ser. No. 15/612,170, filed on Jun. 2, 2017, now U.S.Pat. No. 10,715,267, issued Jul. 14, 2020, which is a continuation ofU.S. patent application Ser. No. 15/061,897, filed on Mar. 4, 2016, nowU.S. Pat. No. 9,705,622, issue on Jul. 11, 2017, which claims thebenefit of U.S. Provisional Application No. 62/129,717, filed on Mar. 6,2015, the contents of which are incorporated herein by reference.

BACKGROUND 1. Technical Field

The technology described herein relates generally to wirelessnetworking. More particularly, the technology relates to providingadditional decoding time for symbols that have been transmitted over awireless network.

2. Description of the Related Art

Wireless LAN (WLAN) devices are currently being deployed in diverseenvironments. Some of these environments have large numbers of accesspoints (APs) and non-AP stations in geographically limited areas. Inaddition, WLAN devices are increasingly required to support a variety ofapplications such as video, cloud access, and offloading. In particular,video traffic is expected to be the dominant type of traffic in manyhigh efficiency WLAN deployments. With the real-time requirements ofsome of these applications, WLAN users demand improved performance indelivering their applications, including improved power consumption forbattery-operated devices.

A WLAN is being standardized by the IEEE (Institute of Electrical andElectronics Engineers) Part 11 under the name of “Wireless LAN MediumAccess Control (MAC) and Physical Layer (PHY) Specifications.” A seriesof standards have been adopted as the WLAN evolved, including IEEE Std802.11™-2012 (March 2012) (hereinafter, IEEE Std 802.11). The IEEE Std802.11 was subsequently amended by IEEE Std 802.11ae™-2012, IEEE Std802.11aa™-2012, IEEE Std 802.11ad™-2012, and IEEE Std 802.11ac™-2013(hereinafter, IEEE 802.11ac).

Recently, an amendment focused on providing a high efficiency (HE) WLANin high-density scenarios is being developed by the IEEE 802.11ax taskgroup. The 802.11ax amendment focuses on improving metrics that reflectuser experience, such as average per station throughput, the 5thpercentile of per station throughput of a group of stations, and areathroughput. Improvements will be made to support environments such aswireless corporate offices, outdoor hotspots, dense residentialapartments, and stadiums.

Included in the focus of the 802.11ax amendment is power-efficientoperation of battery-power WLAN devices. Such battery-powered devicesmay have substantially less processing power than typical line-powereddevices.

A frame transmitted in next-generation WLAN technology, such as802.11ax, may be transmitted using a symbol having a longer durationthan symbols used in current WLAN technology such as IEEE 802.11ac. Forexample, a symbol in an IEEE 802.11ac WLAN may have a symbol duration of3.2 microseconds (μs), whereas a symbol in an IEEE 802.11ax WLAN mayhave a symbol duration of 12.8 μs. The symbol in IEEE 802.11ax WLAN mayalso be transmitted using more subcarriers than the symbol in the IEEE802.11ac WLAN.

The amount of information encoded into a symbol may be proportional tothe duration of the symbol and to the number of subcarriers used totransmit the symbol. Accordingly, a symbol having a duration of 12.8 μsmay include four times the information of a symbol having a duration of3.2 μs. Because the amount of processing time needed to decode a symbolmay increase as the amount of information included in the symbolincreases, a symbol having a duration of 12.8 μs may take longer todecode than a symbol having a duration of 3.2 μs.

The decoding of a symbol may not begin until the entire symbol has beenreceived.

Space-Time Block Coding (STBC) may also be employed when transmittinginformation over the WLAN. In STBC, first and second received versionsof a symbol may be combined to decode the symbol. The first version maycorrespond to an encoding of data, and the second version may correspondto an encoding of a complex conjugate of the data.

The first and second received versions of the symbol may be receivedconsecutively. The decoding of a symbol transmitted using STBC may notbegin until after the entirety of both versions of the symbol has beenreceived.

A receiving device that receives a frame over the WLAN may be requiredto transmit a response, such as an Acknowledgement (ACK) frame, within apredetermined time after the end of the received frame. The receivingdevice may be required to completely decode the received frame beforetransmitting the response.

When a symbol duration of received frames is increased, STBC is used toencode the received frame, or both, the amount of processing required todecode the final symbol(s) of the received frame may increase. As aresult, it may not be possible for some receiving devices, such asbattery-powered receiving devices, to complete decoding of the finalsymbols(s) of the received frame in the time allowed by current WLANtechnologies.

SUMMARY

In an embodiment, a method of a communication device in a wirelesssystem comprises generating a High Efficiency Physical Layer ConvergenceProcedure (PLCP) Protocol Data Unit (HE PPDU) frame including (i) anOrthogonal Frequency Division Multiplexing (OFDM) symbol includingpadding bits and (ii) an extension having a non-zero signal strength.The method further comprises transmitting the HE PPDU frame.

In an embodiment, a High Efficiency signal (HE-SIG) field of the HE PPDUframe includes an indication for a duration of the extension to avoidambiguity of the extension.

In an embodiment, the indication indicates whether the duration of theextension is greater than a predetermined duration.

In an embodiment, the extension supports plural durations which are amultiple of a unit of time.

In an embodiment, the unit of time is 4 microseconds.

In an embodiment, the plural durations include 0, 4, 8, 12, and 16microseconds.

In an embodiment, the HE PPDU frame further includes a Non-HT signal(L-SIG) field indicating an end of the extension.

In an embodiment, the L-SIG field includes an L-SIG length fieldindicating the end of the extension.

In an embodiment, the padding bits are appended after an encoding stageencoding a MAC frame.

In an embodiment, the OFDM symbol has a symbol duration of 12.8microsecond excluding a cyclic prefix.

In an embodiment, the OFDM symbol supports plural cyclic prefixdurations of 0.8, 1.6, and 3.2 microseconds.

In an embodiment, a method of a first communication device in a wirelesssystem comprises receiving a High Efficiency Physical Layer ConvergenceProcedure (PLCP) Protocol Data Unit (HE PPDU) frame including (i) anOrthogonal Frequency Division Multiplexing (OFDM) symbol includingpadding bits, and (ii) an extension having a non-zero signal strength,and transmitting an Acknowledgement frame a predetermined inter-framespace after an end of the HE PPDU frame.

In an embodiment, a High Efficiency signal (HE-SIG) field of the HE PPDUincludes an indication for duration of the extension to avoid ambiguityof the extension.

In an embodiment, the indication indicates whether the duration of theextension is greater than a predetermined duration.

In an embodiment, the extension supports plural durations which are amultiple of a unit of time.

In an embodiment, the unit of time is 4 microseconds.

In an embodiment, the plural durations include 0, 4, 8, 12, and 16microseconds.

In an embodiment, the HE PPDU frame further includes a Non-HT signal(L-SIG) field including a L-SIG length field indicating an end of theextension.

In an embodiment, the OFDM symbol has a symbol duration of 12.8microsecond excluding a cyclic prefix, and supports plural cyclic prefixdurations of 0.8, 1.6, and 3.2 microseconds.

In an embodiment, the predetermined inter-frame space is 16microseconds.

In an embodiment, a method of a communication device comprisesgenerating capability information of the communication device. Thecapability information indicates a required additional processing timewhich is to be provided by (i) first padding bits of a High EfficiencyPhysical Layer Convergence Procedure (PLCP) Protocol Data Unit (HE PPDU)frame and (ii) an extension of the HE PPDU frame. The method furthercomprises transmitting the capability information.

In an embodiment, the required additional processing time corresponds toone or more transmission types.

In an embodiment, the one or more transmission types includes abandwidth.

In an embodiment, the one or more transmission types further includes amodulation type.

In an embodiment, a MAC frame included in the HE PPDU frame is encodedusing an encoding stage, and the first padding bits are not encodedusing the encoding stage.

In an embodiment, the first padding bits correspond to bits appendedafter the encoding stage.

In an embodiment, the encoding stage uses a Forward Error Correction(FEC) encoder.

In an embodiment, a duration of the extension is a multiple of 4microseconds.

In an embodiment, the extension has a non-zero signal strength.

In an embodiment, the method of claim further comprises receiving the HEPPDU frame including (i) an Orthogonal Frequency Division Multiplexing(OFDM) symbol including the first padding bits, and (ii) the extension,and transmitting an Acknowledgement frame a predetermined inter-framespace after an end of the HE PPDU frame.

In an embodiment, the HE PPDU frame further includes second padding bitsthat are appended prior to an encoding stage.

In an embodiment, the HE PPDU frame further includes an indicationindicating the first padding bits.

In an embodiment, the OFDM symbols have a symbol duration of 12.8microsecond excluding a cyclic prefix.

In an embodiment, the OFDM symbol supports plural cyclic prefixdurations of 0.8, 1.6, and 3.2 microseconds.

In an embodiment, the predetermined inter-frame space is 16microseconds.

In an embodiment, a method of a first communication device comprisesreceiving capability information of a second communication device. Thecapability information indicates an additional processing time which isto be provided by (i) first padding bits of a

High Efficiency Physical Layer Convergence Procedure (PLCP) ProtocolData Unit (HE PPDU) frame and (ii) an extension of the HE PPDU frame.The method further comprises generating the HE PPDU frame including (i)an Orthogonal Frequency Division Multiplexing (OFDM) symbol includingthe first padding bits and (ii) the extension, and transmitting the HEPPDU frame.

In an embodiment, the additional processing time corresponds to one ormore transmission types.

In an embodiment, the one or more transmission types includes abandwidth.

In an embodiment, the one or more transmission types further includes amodulation type.

In an embodiment, the method further comprises appending second paddingbits prior to an encoding stage. The first padding bits are appendedafter the encoding stage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless network according to an embodiment.

FIG. 2 is a schematic diagram of a wireless device according to anembodiment.

FIG. 3A illustrates components of a wireless device configured totransmit data according to an embodiment.

FIG. 3B illustrates components of a wireless device configured toreceive data according to an embodiment.

FIG. 4A illustrates a WLAN operation between a first station and asecond station according to an embodiment.

FIG. 4B illustrates details of the WLAN operation of FIG. 4A during aperiod between a first time T1 and a second time T2.

FIG. 5 illustrates a technology for increasing an available decode timeof a symbol according to an embodiment.

FIG. 6 illustrates a technology for increasing an available decode timeof a symbol according to another embodiment.

FIG. 7 illustrates a technology for increasing an available decode timeof a symbol according to another embodiment.

FIG. 8 illustrates a technology for increasing an available decode timeof a symbol according to another embodiment.

FIG. 9 illustrates a process for increasing an available decode time ofa symbol encoded into a transmitted frame, according to an embodiment.

FIG. 10 illustrates a process of receiving and processing a frame havingan extended duration, according to an embodiment.

FIG. 11 illustrates a process for extending a duration of a frameaccording to an embodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate generally to wirelessnetworking, and more particularly, to increasing an available decodetime (that is, an amount of time available to decode and process) of asymbol that has been received over a wireless network.

In the following detailed description, certain illustrative embodimentshave been illustrated and described. As those skilled in the art wouldrealize, these embodiments may be modified in various different wayswithout departing from the scope of the present disclosure. Accordingly,the drawings and description are to be regarded as illustrative innature and not restrictive. Like reference numerals designate likeelements in the specification.

FIG. 1 illustrates a wireless network according to an embodiment. Thewireless network includes an infrastructure Basic Service Set (BSS) 100of a Wireless Local Area Network (WLAN). In an 802.11 wireless LAN, theBSS provides the basic building-block and typically includes an accesspoint (AP) and one or more associated stations (STAs). In FIG. 1 , theBSS 100 includes an Access Point 102 (also referred to as AP) wirelesslycommunicating with first, second, third, and fourth wireless devices (orstations) 104, 106, 108, and 110 (also referred to as STA1, STA2, STA3,and STA4, respectively). The wireless devices may each include a mediumaccess control layer (MAC) and a physical layer (PHY) according to anIEEE 802.11 standard.

Although the example of FIG. 1 shows only the BSS 100 including only thefirst to fourth stations STA1 to STA4, embodiments are not limitedthereto and may comprise BSSs including any number of STAs.

The AP 102 is a station, that is, a STA, configured to control andcoordinate functions of the BSS 100. The AP 102 may transmit informationto a single station selected from the plurality of stations STA1 to STA4in the BSS 100 using a single frame, or may simultaneously transmitinformation to two or more of the stations STA1 to STA4 in the BSS 100using either a single Orthogonal Frequency Division Multiplexing (OFDM)broadcast frame, a single OFDM Multi-User Multi-Input-Multi-Output(MU-MIMO) transmission, or a single Orthogonal Frequency DivisionMultiple Access (OFDMA) frame.

The stations STA1 to STA4 may each transmit data to the AP 102 using asingle frame, or transmit information to and receive information fromeach other using a single frame. Two or more of the stations STA1 toSTA4 may simultaneously transmit data to the AP 102 using an Uplink (UL)OFDMA frame. When the BSS 100 supports Spatial Division Multiple Access(SDMA), two or more of the stations STA1 to STA4 may simultaneouslytransmit data to the AP 102 using an UL MU-MIMO frame.

In another embodiment, the AP 102 may be absent and the stations STA1 toSTA4 may be in an ad-hoc network.

Each of the stations STA1 to STA4 and the AP 102 includes a processorand a transceiver, and may further include a user interface and adisplay device.

The processor is configured to generate a frame to be transmittedthrough a wireless network, to process a frame received through thewireless network, and to execute protocols of the wireless network. Theprocessor may perform some or all of its functions by executing computerprogramming instructions stored on a non-transitory computer-readablemedium. The transceiver represents a unit functionally connected to theprocessor, and designed to transmit and receive a frame through thewireless network.

The transceiver may include a single component that performs thefunctions of transmitting and receiving, or two separate components eachperforming one of such functions. The processor and the transceiver maybe implemented in each of the stations STA1 to STA4 and the AP 102 usingrespective hardware components, software components, or both.

The AP 102 may be or may include a WLAN router, a stand-alone AccessPoint, a WLAN bridge, a Light-Weight Access Point (LWAP) managed by aWLAN controller, and the like. In addition, a device such as a personalcomputer, tablet computer, or cellular phone may be able to operate asthe AP 102, such as when a cellular phone is configured to operate as awireless “hot spot.”

Each of the stations STA1 to STA4 may be or may include a desktopcomputer, a laptop computer, a tablet PC, a wireless phone, a mobilephone, a smart phone, an e-book reader, a Portable Multimedia Player(PMP), a portable game console, a navigation system, a digital camera, aDigital Multimedia Broadcasting (DMB) player, a digital audio recorder,a digital audio player, a digital picture recorder, a digital pictureplayer, a digital video recorder, a digital video player, and the like.

The present disclosure may be applied to WLAN systems according to IEEE802.11 standards but is not limited thereto.

In IEEE 802.11 standards, frames exchanged between stations (includingaccess points) are classified into management frames, control frames,and data frames. A management frame may be a frame used for exchangingmanagement information that is not forwarded to a higher layer of acommunication protocol stack. A control frame may be a frame used forcontrolling access to a medium. A data frame may be a frame used fortransmitting data to be forwarded to the higher layer of thecommunication protocol stack.

Each frame's type and subtype may be identified using a type field and asubtype field included in a control field of the frame, as prescribed inthe applicable standard.

FIG. 2 illustrates a schematic block diagram of a wireless device 200according to an embodiment. The wireless or WLAN device 200 canrepresent any device in a BSS, e.g., the AP 102 or any of the stationsSTA1 to STA4 in FIG. 1 . The WLAN device 200 includes a basebandprocessor 210, a radio frequency (RF) transceiver 240, an antenna unit250, a storage device (e.g., memory) 232, one or more input interfaces234, and one or more output interfaces 236. The baseband processor 210,the memory 232, the input interfaces 234, the output interfaces 236, andthe RF transceiver 240 may communicate with each other via a bus 260.

The baseband processor 210 performs baseband signal processing, andincludes a MAC processor 212 and a PHY processor 222. The basebandprocessor 210 may utilize the storage device 232, which may include anon-transitory computer readable medium having software (e.g., computerprograming instructions) and data stored therein.

In an embodiment, the MAC processor 212 includes a MAC softwareprocessing unit 214 and a MAC hardware processing unit 216. The MACsoftware processing unit 214 may implement a first plurality offunctions of the MAC layer by executing MAC software, which may beincluded in the software stored in the storage device 232. The MAChardware processing unit 216 may implement a second plurality offunctions of the MAC layer in special-purpose hardware, hereinafterreferred to as “MAC hardware.” However, the MAC processor 212 is notlimited thereto. For example, the MAC processor 212 may be configured toperform the first and second plurality of functions entirely in softwareor entirely in hardware according to an implementation.

The PHY processor 222 includes a transmitting signal processing unit 224and a receiving signal processing unit 226. The PHY processor 222implement a plurality of functions of the PHY layer. These functions maybe performed in software, hardware, or a combination thereof accordingto implementation.

Functions performed by the transmitting signal processing unit 224 mayinclude one or more of Forward Error Correction (FEC) encoding, streamparsing into one or more spatial streams, diversity encoding of thespatial streams into a plurality of space-time streams, spatial mappingof the space-time streams to transmit chains, inverse Fourier Transform(iFT) computation, Cyclic Prefix (CP) insertion to create a GuardInterval (GI), and the like.

The RF transceiver 240 includes an RF transmitter 242 and an RF receiver244. The RF transceiver 240 is configured to transmit first informationreceived from the baseband processor 210 to the WLAN, and provide secondinformation received from the WLAN to the baseband processor 210.

The antenna unit 250 includes one or more antennas. When Multiple-InputMultiple-Output (MIMO) or Multi-User MIMO (MU-MIMO) is used, the antennaunit 250 may include a plurality of antennas. In an embodiment, theantennas in the antenna unit 250 may operate as a beam-formed antennaarray. In an embodiment, the antennas in the antenna unit 250 may bedirectional antennas, which may be fixed or steerable.

The input interfaces 234 receive information from a user, and the outputinterfaces 236 output information to the user. The input interfaces 234may include one or more of a keyboard, keypad, mouse, touchscreen, touchscreen, microphone, and the like. The output interfaces 236 may includeone or more of a display device, touch screen, speaker, and the like.

As described herein, many functions of the WLAN device 200 may beimplemented in either hardware or software. Which functions areimplemented in software and which functions are implemented in hardwarewill vary according to constraints imposed on a design. The constraintsmay include one or more of design cost, manufacturing cost, time tomarket, power consumption, available semiconductor technology, and soon.

As described herein, a wide variety of electronic devices, circuits,firmware, software, and combinations thereof may be used to implementthe functions of the components of the WLAN device 200. Furthermore, theWLAN device 200 may include other components, such as applicationprocessors, storage interfaces, clock generator circuits, power supplycircuits, and the like, which have been omitted in the interest ofbrevity.

FIG. 3A illustrates components of a wireless device configured totransmit data according to an embodiment, including a Transmitting (Tx)Signal Processing Unit (TxSP) 324, an RF transmitter 342, and an antenna352. In an embodiment, the TxSP 324, the RF transmitter 342, and theantenna 352 correspond to the transmitting signal processing unit 224,the RF transmitter 242, and an antenna of the antenna unit 250 of FIG. 2, respectively.

The TxSP 324 includes an encoder 300, an interleaver 302, a mapper 304,an inverse Fourier transformer (IFT) 306, and a guard interval (GI)inserter 308.

The encoder 300 receives and encodes input data DATA. In an embodiment,the encoder 300 includes a forward error correction (FEC) encoder. TheFEC encoder may include a binary convolutional code (BCC) encoderfollowed by a puncturing device. The FEC encoder may include alow-density parity-check (LDPC) encoder.

The TxSP 324 may further include a scrambler for scrambling the inputdata before the encoding is performed by the encoder 300 to reduce theprobability of long sequences of 0s or 1s. When the encoder 300 performsthe BCC encoding, the TxSP 324 may further include an encoder parser fordemultiplexing the scrambled bits among a plurality of BCC encoders. IfLDPC encoding is used in the encoder, the TxSP 324 may not use theencoder parser.

The interleaver 302 interleaves the bits of each stream output from theencoder 300 to change an order of bits therein. The interleaver 302 mayapply the interleaving only when the encoder 300 performs the BCCencoding, and otherwise may output the stream output from the encoder300 without changing the order of the bits therein.

The mapper 304 maps the sequence of bits output from the interleaver 302to constellation points. If the encoder 300 performed LDPC encoding, themapper 304 may also perform LDPC tone mapping in addition to theconstellation mapping.

When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324may include a plurality of interleavers 302 and a plurality of mappers304 according to a number NSS of spatial streams of the transmission.The TxSP 324 may further include a stream parser for dividing the outputof the encoder 300 into blocks and may respectively send the blocks todifferent interleavers 302 or mappers 304. The TxSP 324 may furtherinclude a space-time block code (STBC) encoder for spreading theconstellation points from the spatial streams into a number NSTS ofspace-time streams and a spatial mapper for mapping the space-timestreams to transmit chains. The spatial mapper may use direct mapping,spatial expansion, or beamforming.

The IFT 306 converts a block of the constellation points output from themapper 304 (or, when MIMO or MU-MIMO is performed, the spatial mapper)to a time domain block (i.e., a symbol) by using an inverse discreteFourier transform (IDFT) or an inverse fast Fourier transform (IFFT). Ifthe STBC encoder and the spatial mapper are used, the IIFT 306 may beprovided for each transmit chain.

When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324may insert cyclic shift diversities (CSDs) to prevent unintentionalbeamforming. The TxSP 324 may perform the insertion of the CSD before orafter the IFT 306. The CSD may be specified per transmit chain or may bespecified per space-time stream. Alternatively, the CSD may be appliedas a part of the spatial mapper.

When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocksbefore the spatial mapper may be provided for each user.

The GI inserter 308 prepends a GI to each symbol produced by the IFT306. Each GI may include a Cyclic Prefix (CP) corresponding to arepeated portion of the end of the symbol the GI precedes. The TxSP 324may optionally perform windowing to smooth edges of each symbol afterinserting the GI.

The RF transmitter 342 converts the symbols into an RF signal andtransmits the RF signal via the antenna 352. When the TxSP 324 performsa MIMO or MU-MIMO transmission, the GI inserter 308 and the RFtransmitter 342 may be provided for each transmit chain.

FIG. 3B illustrates components of a wireless device configured toreceive data according to an embodiment, including a Receiver (Rx)Signal Processing Unit (RxSP) 326, an RF receiver 344, and an antenna354. In an embodiment, the RxSP 326, RF receiver 344, and antenna 354may correspond to the receiving signal processing unit 226, the RFreceiver 244, and an antenna of the antenna unit 250 of FIG. 2 ,respectively.

The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316,a demapper 314, a deinterleaver 312, and a decoder 310.

The RF receiver 344 receives an RF signal via the antenna 354 andconverts the RF signal into symbols. The GI remover 318 removes the GIfrom each of the symbols. When the received transmission is a MIMO orMU-MIMO transmission, the RF receiver 344 and the GI remover 318 may beprovided for each receive chain.

The FT 316 converts each symbol (that is, each time domain block) into afrequency domain block of constellation points by using a discreteFourier transform (DFT) or a fast Fourier transform (FFT). The FT 316may be provided for each receive chain.

When the received transmission is the MIMO or MU-MIMO transmission, theRxSP 326 may include a spatial demapper for converting the respectiveoutputs of the FTs 316 of the receiver chains to constellation points ofa plurality of space-time streams, and an STBC decoder for despreadingthe constellation points from the space-time streams into one or morespatial streams.

The demapper 314 demaps the constellation points output from the FT 316or the STBC decoder to bit streams. If the received transmission wasencoded using the LDPC encoding, the demapper 314 may further performLDPC tone demapping before performing the constellation demapping.

The deinterleaver 312 deinterleaves the bits of each stream output fromthe demapper 314. The deinterleaver 312 may perform the deinterleavingonly when the received transmission was encoded using the BCC encoding,and otherwise may output the stream output by the demapper 314 withoutperforming deinterleaving.

When the received transmission is the MIMO or MU-MIMO transmission, theRxSP 326 may use a plurality of demappers 314 and a plurality ofdeinterleavers 312 corresponding to the number of spatial streams of thetransmission. In this case, the RxSP 326 may further include a streamdeparser for combining the streams output from the deinterleavers 312.

The decoder 310 decodes the streams output from the deinterleaver 312 orthe stream deparser. In an embodiment, the decoder 312 includes an FECdecoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

The RxSP 326 may further include a descrambler for descrambling thedecoded data. When the decoder 310 performs the BCC decoding, the RxSP326 may further include an encoder deparser for multiplexing the datadecoded by a plurality of BCC decoders. When the decoder 310 performsthe LDPC decoding, the RxSP 326 may not use the encoder deparser.

FIG. 4A illustrates a WLAN operation 400 between a first station STA1and a second station STA2 according to an embodiment. The operationincludes a Ready-To-Send (RTS) frame 402, a Clear-To-Send (CTS) frame404, a Physical Layer Convergence Procedure (PLCP) Protocol Data Unit(PPDU) frame 406, and an Acknowledgment (ACK) frame 408.

The WLAN operation 400 may utilize a Distributed Coordination Function(DCF). One or more of the stations STA1 to STA3 may be Access Points.

The first station STA1 transmits the RTS frame 402. In the example ofFIG. 4A, the RTS frame 402 is addressed to the second station STA2 andnot addressed to the third station STA3.

The second station STA2 receives and decodes the RTS frame 402. When thesecond station STA2 determines that the RTS frame 402 is addressed tothe second station STA2, the second station STA2 responds to the RTSframe 402, after a first Sort Inter-Frame Space (SIFS) having a durationequal to an SFIS duration t_(SIFS), by transmitting the CTS frame 404addressed to the first station STA1. The SIFS duration t_(SIFS) ismeasured from the end of a prior transmission in the channel to thebeginning of a next transmission in the channel.

The third station STA3 also receives and decodes the RTS frame 402. Whenthe third station STA3 determines that the RTS frame 402 is notaddressed to the third station STA3, the third station STA3 sets aNetwork Allocation Vector (NAV) 410 according to a duration valueincluded in the RTS frame 402. The NAV 410 is used to reserve thechannel for the remainder of the WLAN operation 400.

The value set in the NAV 410 corresponds to a period of time, beginningwhen the NAV 410 is set, during which the third station STA3 will nottransmit to the channel and, in an embodiment, may not sense thechannel. The period of time may correspond to a sum of a duration of theCTS frame 404, a duration of the PPDU frame 406, a duration of the ACKframe 408, and three times the SFIS duration t_(SIGS).

Depending on the geographic layout and other factors, the third stationSTA3 may or may not receive the CTS frame 404. When the third stationSTA3 receives the CTS frame 404 (not shown in FIG. 4A) and determinesthat the CTS frame 404 is not addressed to the third station STA3, thethird station STA3 may update the NAV 410 according to a duration valueincluded in the CTS frame 404.

After the period of time set in the NAV 410, the third station STA3continues to not transmit for at least an additional DistributedCoordination Function (DCF) InterFrame Space (DIFS) having a durationequal to a DIFS duration t_(DIFS). The DIFS duration t_(DIFS) may be oneof 28, 34, and 50 microseconds.

During the DIFS, the third station STA3 may sense the channel todetermine whether the channel is in use. After the DIFS, the thirdstation STA3 may transmit to the channel after a backoff period of 0 ormore time slots.

When the first station STA1 receives and decodes the CTS frame 404, thenafter a second SIFS the first station STA1 transmits the PPDU frame 406.The PPDU frame 406 is addressed to the second station STA2.

The second station STA2 receives and decodes the PPDU frame 406. Inresponse, after a third SIFS having a duration equal to the SFISduration t_(SIFS), the second station STA2 responds to the PPDU frame406 by transmitting the ACK frame 408 addressed to the first stationSTA1.

If the second station STA2 fails to begin transmitting the ACK frame 408at the end of the third SIFS, the first station STA1 may determine thattransmission of the PPDU frame 406 has failed. When the first stationSTA1 determines that transmission of the PPDU frame 406 has failed, thefirst station STA1 may re-transmit the PPDU frame 406.

When the NAV 410 only reserves the channel for the WLAN operation 400until a calculated end time of the transmission of the ACK frame 408, asshown in FIG. 4A, the second station STA2 must complete transmission ofthe ACK frame 408 before the period of time set in the NAV vectorexpires.

The second station STA2 is therefore required to start transmitting theACK frame 408 one SIFS after the transmission of the PPDU frame 406 iscomplete. The second station STA2 must receive and successfully decodeall valid data-carrying symbols of the PPDU frame 406 before beginningtransmission of the ACK frame 408.

FIG. 4B illustrates details of the WLAN operation 400 of FIG. 4A duringa period between a first time T1 and a second time T2. FIG. 4Billustrates a final portion of the PPDU frame 406 and an initial portionof the ACK frame 408.

The PPDU frame 406 includes a sequence of data symbols including athird-to-last symbol 414, a second-to-last symbol 418, and a last symbol422. In an embodiment, the symbols 414, 418, and 422 are OFDM symbols.

Each symbol is preceded by a Cyclic Prefix (CP) that occupies a GuardInterval (GI): the third-to-last symbol 414 is preceded by athird-to-last CP 412, the second-to-last symbol 418 is preceded by asecond-to-last CP 416, and the last symbol 422 is preceded by a last CP420.

Each data symbol in the PPDU frame 406 has a duration equal to a symbolduration t_(SYM). In an embodiment, the symbol duration t_(SYM) is 12.8microseconds. Each data symbol has 78.125 kHz subcarrier spacing. EachCP in the PPDU frame 406 has a duration equal to a CP duration t_(CP).In an embodiment, the CP duration t_(CP) may be one of 0.8, 1.6, and 3.2microseconds.

As explained with reference to FIG. 4A, the second station STA2 may berequired to finish decoding and determining the validity of the PPDUframe 406 before the end of an SIFS of 16 microseconds, the SIFSbeginning when transmission of the PPDU frame 406 is complete. In anembodiment according to the IEEE 802.11b standard for a 2.4 GHz band,the second station STA2 may be required to finish decoding anddetermining validity of the PPDU frame 406 during a SIFS of 10microseconds plus a Signal Extension time of 16 microseconds.Hereinafter, both the SIFS of 16 microseconds and the IEEE 802.11bSIFS+Signal Extension of 16 microseconds are referred to as the16-microsecond SIFS.

Hereinafter, the interval between a time when a receiving devicefinishes receiving a final symbol that must be decoded and a time whenthe receiving device must begin transmitting a correspondingacknowledgment is referred to as an available decode time t_(dec).

When the second station STA2 uses a pipelined implementation capable ofprocessing one or more prior-received symbols while receiving a latersymbol, the last or last few OFDM symbol(s) of the received PPDU frame406 may be the most problematic. A time necessary to complete processingof the last or last few OFDM symbol(s) of the received PPDU frame 406may determine the earliest time at which the second station STA2 may beready to transmit the ACK frame 408.

Processing of the last symbol 422 may begin when the entirety of thelast symbol 422 has been received. As a result, within the16-microsecond SIFS, the second station STA2 may be required to processthe last symbol 422 by performing, for example, frequency offsetcompensation, FFT, equalization, de-interleaving, de-rate-matching,decoding, frame checksum computation, and additional operations asdescribed with reference to FIG. 3 .

When processing the last symbol 422 does not rely on combining the lastsymbol 422 with any other symbol, such as when STBC is not used totransmit the last symbol 422, the earliest time which the second stationSTA2 may be ready to transmit the ACK frame 408 may depend on the timenecessary to process the information in the last symbol 422.

An increases in the amount of information in the last symbol 422 (suchas when the duration of the last symbol 422, the number of carriers usedto transmit the last symbol 422, or both are increased) may increase thetime necessary to process the information in the last symbol 422. Forexample, a symbol transmitted according to the 802.11ax amendment thathas a duration of 12.8 microseconds may require processing equivalent toprocessing four symbols transmitted according to the IEEE Std 802.11acthat each have a duration of 3.2 microseconds. This increase in therequired processing may cause a corresponding delay in the earliest timeat which the second station STA2 may be ready to transmit the ACK frame408.

When processing the last symbol 422 does rely on combining the lastsymbol 422 with another symbol, the time necessary to process theinformation in the last symbol 422 may increase.

For example, when STBC is used to transmit the PPDU frame 406, decodingthe last symbol 422 may use information from both the last symbol 422and the next to last symbol 418, and the time necessary to process theinformation in the combined information may be substantially longer(e.g., twice as long) than the time necessary to process the informationin the last symbol 422 alone. More specifically, a pair of symbolsaccording to the 802.11ax amendment that are transmitted utilizing STBCand that each have a duration of 12.8 microseconds may together requireprocessing equivalent to processing eight 3.2 microseconds IEEE Std802.11ac symbols transmitted without STBC.

Because the processing of the next to last symbol 418 and the lastsymbol 422 may not start before the entirety of the last symbol 422 hasbeen received, this increase in the required processing may causefurther delay in the earliest time at which the second station STA2 maybe ready to transmit the ACK frame 408.

To meet the requirement to timely transmit the ACK frame 408 insituations where additional processing is required after reception ofthe last symbol 422, a receiving device may be supplied with morecircuits to perform the processing, faster circuits to perform theprocessing, or both. However, in devices that are battery-powered,cost-sensitive, or both, providing more circuits, faster circuits, orboth may be undesirable.

Accordingly, embodiments of the present disclosure relate to providingmore time for receiving devices (such as the second station STA2) toperform the processing of one or more final decoded symbols of a framesuch as the PPDU frame 406.

FIGS. 5-8 each illustrate a technology for increasing an availabledecode time t_(dec) of a symbol according to embodiments. Each of thetechnologies illustrated in FIGS. 5-8 may be use alone or in combinationwith one or more of the other technologies.

FIG. 5 illustrates a portion of a WLAN operation 500 during a periodcorresponding to reception of a final portion of a PPDU frame 506 andthe beginning of transmission of an ACK frame 508 responsive to the PPDUframe 506, according to an embodiment. In the WLAN operation 500, afirst station STA1 transmits the PPDU frame 506 and a second stationSTA2 receives the PPDU frame 506. The WLAN operation 500 may beperformed when the first station STA1 has determined that the secondstation STA2 needs additional processing time to process the finalsymbol containing data of the PPDU frame 506.

FIG. 5 also illustrates a final portion of an Aggregate MAC ProtocolData Unit (A-MPDU) 526 corresponding to the PPDU frame 506. The A-MPDU526 includes a Data MPDU 530, a first End-of-Frame (EOF) MPDU 532, asecond EOF MPDU 534, a third EOF MPDU 536, and a fourth EOF MPDU 538.

A second to last portion of the Data MPDU 530 is encoded into a third tolast symbol 514 of the PPDU frame 506, as indicated by the dashed linesin FIG. 5 . A last portion of the Data MPDU 530 and the first EOF MPDU532 are both encoded into a second to last symbol 518 of the PPDU frame506. The second EOF MPDU 534, third EOF MPDU 536, and fourth EOF MPDU538 are encoded into a last symbol 522 of the PPDU frame 506. Thesymbols 514, 518, and 522 may each be OFDM symbols.

Although FIG. 5 shows three EOF MPDUs being encoded into a singlesymbol, embodiments are not limited thereto. And although FIG. 5 showsthe entirety of each EOF MPDU being encoded into a single symbol,embodiments are not limited thereto, and in an embodiment a firstportion of an EOF MPDU may be encoded into a first symbol and a secondportion of the EOF MPDU may be encoded into a next symbol transmittedimmediately after the first symbol.

Each symbol of the PPDU frame 506 is preceded by a Cyclic Prefix (CP)that occupies a Guard Interval (GI), so that the third-to-last symbol514 is preceded by a third-to-last CP 512, the second-to-last symbol 518is preceded by a second-to-last CP 516, and the last symbol 522 ispreceded by a last CP 520.

Each of the EOF MPDUs 532, 534, 536, and 538 include a respective EOFindication. In an illustrative embodiment, each of the EOF MPDUs 532,534, 536, and 538 may be a Null subframe, each Null subframe includingan MPDU delimiter with an EOF field set to 1. The EOF field being set to1 indicates to a receiving device that all of the non-Null MPDUs in theA-MPDU 526 have been received.

When the second station STA2 decodes the second to last symbol 518 ofthe PPDU frame 506, the second station STA2 may the extract the finalportion of the Data MPDU 530 and the first EOF MPDU 532 from the secondto last symbol 518. When the first EOF MPDU 532 includes an EOFindication, such as an MPDU delimiter with an EOF field set to 1, thesecond station STA2 may determine that the last symbol 538 does not needto be decoded.

As a result, the available decode time t_(dec) for the second stationSTA2 to decode the final symbol of the PPDU frame 506 that is to bedecoded (i.e., the last symbol with data, which in this example issecond to last symbol 518) is increased. In the example shown in FIG. 5, the available decode time t_(dec) increases to a sum of the SIFSduration t_(SIFS), a symbol duration t_(SYM), and a CP duration t_(CP).

For example, when the SIFS duration t_(SIFS) is 16 microseconds, thesymbol duration t_(SYM) is 12.8 microseconds, and the CP durationt_(CP), the available decode time t_(dec) increases from 16 microsecondsto 32 microseconds. However, embodiments are not limited thereto, andthe final symbol of the PPDU frame 506 that is to be decoded maycorrespond to a symbol prior to the second to the last symbol 518 by theaddition of additional symbols including EOF MPDUs to the end of theA-MPDU 526.

Thus, as shown in FIG. 5 , in order to provide more time for thereceiver (second station STA2), the transmitter (the first station STA1)can, at the MAC layer, pad one or more extra data units (such as MPDUs)that do not need to be decoded at the receiver. Because bits in the MAClayer are encoded by an encoding stage (such as a FEC stage), MACpadding occurs prior to the encoding stage, so the MAC padding can becalled pre-encoding padding or pre-FEC padding. In an embodiment, theextra data units may be one or more EOF MPDU in an A-MPDU transmission.The receiver may determine that one or more OFDM symbols do not needdecoding by detecting an EOF MPDU in an OFDM symbol received prior tothe one or more OFDM symbols that do not need decoding.

In an embodiment, when an A-MPDU is transmitted using STBC, the numberof OFDM symbols used to transmit data in the A-MPDU is a multiple oftwo. However, when the last symbol used to transmit the A-MPDU containsonly padding that does not need decoding by the receiver, the lastsymbol used to transmit the A-MPDU may be a single OFDM symbol that isnot paired with another OFDM symbol.

A device receiving a frame that detects an EOF MPDU in the frame maydetermine to not decode any OFDM symbols that follow an OFDM symbol thatincluded the EOF MPDU.

In an embodiment, the receiving device may detect the EOF MPDU afterreception of the entire EOF MPDU, including frame check sum (FCS) bitsassociated with the EOF MPDU. When transmitting to the receiving deviceof this embodiment, a device transmitting the frame including the EOFMPDU may pad the transmitted information so that a first EOF MPDU in theframe is transmitted in its entirety before the beginning of the OFDMsymbol or symbols that do not need decoding. That is, the first EOF MPDUis transmitted in its entirety before the beginning of the last OFDMsymbol or, when the receiving device needs more than one symbol durationt_(SYM) of decoding processing time relaxation, before a plurality offinal OFDM symbols.

In another embodiment, the receiving device may detect the EOF MPDU whenthe header of the EOF MPDU is decoded, even when a final portion of theEOF MPDU was transmitted in an OFDM symbol that has not been decoded.When transmitting to the receiving device of this embodiment, a devicetransmitting the frame including the EOF MPDU may pad the transmittedinformation so that a header portion of a first EOF MPDU in the frame istransmitted in its entirety before the beginning of the OFDM symbol orsymbols that do not need decoding. That is, the header of the first EOFMPDU is transmitted in its entirety before the beginning of the lastOFDM symbol or, when the receiving device needs more than one symbolduration t_(SYM) of decoding processing time relaxation, before aplurality of final OFDM symbols.

FIG. 6 illustrates a portion of a WLAN operation 600 during a periodcorresponding to reception of a final portion of a PPDU frame 606 and abeginning of transmission of an ACK frame 608 responsive to the PPDUframe 606, according to another embodiment. The WLAN operation 600includes the PPDU frame 606 transmitted by a first station STA1 and thecorresponding ACK frame 608 transmitted by a second station STA2.

FIG. 6 also includes first extra PHY padding bits including first andsecond padding bits 640 and 642 which the first station STA1incorporates into the PPDU 606 in the physical layer. The first extraPHY padding bits can occur prior to encoding stage, and it is encoded bythe encoding stage, so the first extra PHY padding bits can be calledpre-encoding PHY padding bits. Because the FEC is used for the encodingstage, the pre-encoding PHY padding bits can be called pre-FEC PHYpadding bits. The pre-FEC MAC padding bits and the pre-FEC PHY paddingbits may be applied before the encoding stage using the FEC encoder.

The PPDU frame 606 includes a sequence of symbols including athird-to-last symbol 612, a second-to-last symbol 618, and a last symbol646. Each symbol is preceded by a Cyclic Prefix (CP) that occupies aGuard Interval (GI): the third-to-last symbol 614 is preceded by athird-to-last CP 612, the second-to-last symbol 618 is preceded by asecond-to-last CP 616, and the last symbol 646 is preceded by a last CP644. In an embodiment, the symbols 614, 618, and 646 are OFDM symbols.

Also illustrated in FIG. 6 is an A-MPDU 626 corresponding to the PPDUframe 606. A second to last portion 628A of the A-MPDU 626 is encodedinto the third to last symbol 614 of the PPDU frame 606.

A last portion 628B of the A-MPDU 626 is encoded into the second to lastsymbol 618 of the PPDU frame 606. First padding bits 640 are alsoencoded into the second to last symbol 618. In an embodiment, the firstpadding bits 640 are added before an encoding process (such as an FECencoding) of the last portion 628B of the A-MPDU 626, and the firstpadding bits 640 are joint encoded with the information in the lastportion 628B.

Second padding bits 642 are encoded into the last symbol 646. The secondpadding bits 642 are added before the encoding process (such as the FECencoding) of the last portion 628B of the A-MPDU 626, and (like thefirst padding bits 640) are jointly encoded with the information in thelast portion 628B.

FIG. 6 shows the first padding bits 640 encoded into second to lastsymbol 618 with information corresponding to a portion of the A-MPDU 626and the second padding bits 642 encoded into the last symbol 646, butembodiments are not limited thereto. In an embodiment, symbols producedusing the first padding bits 640 do not include informationcorresponding to a portion of the A-MPDU 626. In an embodiment, thesecond padding bits 642 are used to produce a plurality of final symbolsof the PPDU 606.

FIG. 7 illustrates a portion of a WLAN operation 700 during a periodcorresponding to a reception of a final portion of a PPDU frame 706 anda beginning of a transmission of an ACK frame 708 responsive to the PPDUframe 706, according to another embodiment. The WLAN operation 700includes the PPDU frame 706 transmitted by a first station STA1 and thecorresponding ACK frame 708 transmitted by a second station STA2.

FIG. 7 also includes second extra PHY padding bits including first andsecond padding bits 740 and 750 which the first station STA1incorporates into the PPDU 706 in a physical (PHY) layer. The secondextra PHY padding bits can be provided as separately encoded bits fromthe frame from the MAC layer like the A-MPDU, while the first extra PHYpadding bits occurs prior to encoding stage. The second extra PHYpadding bits are separate from the A-MPDU and the first extra PHYpadding bits in terms of the encoding stage which joint encodes the MACframe and the first extra PHY padding bits. The second extra PHY paddingbits occur after the encoding stage encoding the MAC frame and the firstextra PHY padding bits, and therefore may be referred to aspost-encoding PHY padding bits. Because the FEC is used for the encodingstage, the post-encoding PHY padding bits can be called post-FEC PHYpadding bits. The post-FEC PHY padding bits may be applied on FECencoded bits.

The PPDU frame 706 includes a sequence of symbols including athird-to-last symbol 712, a second-to-last symbol 718, and a last symbol754. Each symbol is preceded by a Cyclic Prefix (CP) that occupies a GI:the third-to-last symbol 714 is preceded by a third-to-last CP 712, thesecond-to-last symbol 718 is preceded by a second-to-last CP 716, andthe last symbol 754 is preceded by a last CP 752. In an embodiment, thesymbols 714, 718, and 754 are OFDM symbols.

Also illustrated in FIG. 7 is an A-MPDU 726 corresponding to the PPDUframe 706. A second to last portion 728A of the A-MPDU 726 is encodedinto the third to last symbol 714 of the PPDU frame 706.

A last portion 728B of the A-MPDU 726 is encoded into the second to lastsymbol 718 of the PPDU frame 706. First padding bits 740 are also addedinto the second to last symbol 718. The first padding bits 740 are addedafter an encoding process (such as an FEC encoding) of the last portion728B of the A-MPDU 726, and the first padding bits 740 are not jointencoded with information in the last portion 728B.

Second padding bits 750 are added into the last symbol 754. The secondpadding bits 750 are added after the encoding process (such as the FECencoding) of the last portion 728B of the A-MPDU 726, and are notjointly encoded with the information in the last portion 728B. Becausethe second padding bits 750 are not jointly encoded with information ofthe A-MPDU 726, decoding of the A-MPDU 726 may be completely separatefrom decoding of the second padding bits 750, and an amount of timeavailable to decode the A-MPDU 726 may be increased. In particular, anavailable decode time t_(dec) for decoding the second to last symbol 718may be increased.

FIG. 7 shows the second padding bits 750 are added into the last symbol754, but embodiments are not limited thereto. In an embodiment, thesecond padding bits 750 are added into a plurality of final symbols ofthe PPDU 706.

In an embodiment, the first station STA1 may provide the second stationSTA2 with an indication indicating the presence or the amount of thesecond extra padding bits. In an embodiment, the first station STA1 mayprovide an indication to the second station STA2 that the PPDU 706includes additional symbols (such as the last symbol 755) that wereadded in the physical layer and that correspond to the second paddingbits 750.

In an embodiment, the presence in the PPDU 706 of additional symbols(such as the last symbol 755) that were added in the physical layer andthat correspond to second padding bits 750 is prescribed by a standard,such as, for example, the proposed IEEE Std 802.1ax standard.

In an embodiment, because the second station STA2 does not need toperform decoding of the second padding bits 750, the first station STA1may not completely send the last symbol 754, and may instead onlytransmit part of the last symbol 754. In an embodiment, the secondpadding bits 750, the last symbol 754, and the last CP 752 may beomitted, and the last symbol of the PPDU 706 may include a portion ofA-MPDU 726 and the first padding bits 740.

FIG. 8 illustrates a WLAN operation 800 during a period corresponding toreception of a final portion of a PPDU frame 806 and the beginning oftransmission of an ACK frame 808 responsive to the PPDU frame 806,according to another embodiment. The WLAN operation 800 includes thePPDU frame 806 transmitted by a first station STA1 and the correspondingACK frame 808 transmitted by a second station STA2.

The PPDU frame 806 includes a sequence of symbols including asecond-to-last symbol 818 and a last symbol 822. Each symbol is precededby a Cyclic Prefix (CP) that occupies a GI: the second-to-last symbol818 is preceded by a second-to-last CP 816, and the last symbol 822 ispreceded by a last CP 820.

In an embodiment, the symbols 818 and 822 are OFDM symbols.

In an embodiment, symbol durations T_(SYM) of the symbols 818 and 822are each equal to 12.8 microseconds. In an embodiment, CP durationsT_(CP) of the CPs 816 and 820 are each equal to any one of 0.8, 1.6, and3.2 microseconds.

A duration to the End of Frame (EOF) of the PPDU 806 is indicated by aLegacy Signal (L-SIG) field (not shown) of the PPDU 806. The L-SIG fieldincludes a data rate field in bits per 1 second and a length field inbytes, wherein both the data rate field and the length field indicatesthe number of virtual OFDM symbols in the PPDU after the L-SIG field,and each virtual OFDM symbol has a four (4) microsecond durationregardless of a duration of the actual symbols used to transmit the PPDU806. As a result, both the data rate field and the length field can beused to derive the N×4 microsecond duration of the PPDU. The lengthfield of the L-SIG field is a number of bytes in the PPDU 806 after theL-SIG field. For example, the duration to the EOF of the PPDU, relativeto the end of the L-SIG field, may therefore be determined using bydividing the length field multiplied by 8 bits by the data rate fieldmultiplied by 4 microseconds and multiplying the result of the divisionby the 4 microseconds duration of the virtual OFDM symbols.

When a duration of the symbols used to transmit a post-L-SIG-fieldportion of the PPDU 806 is 12.8 microseconds, the L-SIG field may beused to provide additional time to the available decode time t_(dec) forthe last symbol 822 by indicating a duration that does not correspond toan integer number of the symbols used to transmit the post-L-SIG-fieldportion of the PPDU 806. The end of the frame can be extended by usingthe L-SIG length indication. The L-SIG length indicated by the L-SIGfield can indicate the end of the extension added to the end of theframe.

In the example shown in FIG. 8 , the symbol duration T_(SYM) is 12.8microseconds and the CP duration T_(CP) is 3.2 microseconds. Each pairof CP and symbol therefore has a prefixed symbol duration t_(CP+SYM) of16 microseconds, equal to the duration of four 4-microsecond virtualOFDM symbols.

In the example shown FIG. 8 , the L-SIG field indicates a duration tothe EOF that is longer than the duration to the end of the last symbol822 by three 4-microsecond intervals. The three 4-microsecond intervalsrespectively correspond to first, second, and third virtual OFDM symbols860, 862, and 864 of FIG. 8 . The second station STA2 can unambiguouslydetermine the actual duration of the PPDU 806 (that is, the duration tothe end of the last symbol 822) by determining the largest duration,relative to the end of the L-SIG field, that is less than or equal tothe duration indicated by the L-SIG field and that is a multiple of theprefixed symbol duration t_(CP+SYM), which prefixed symbol durationt_(CP+SYM) is 16 microseconds in the example shown.

For example, if the L-SIG field indicates a post-L-SIG-field duration tothe EOF that is 172 microseconds (corresponding to 43 4-microsecondvirtual OFDM symbols), the second station STA2 may unambiguouslydetermine that the actual duration of the post-L-SIG-field portion ofthe PPDU 806 is 160 microseconds and the duration of the extension ofthe PPDU 806 is 12 microseconds, because the 160-microsecond durationcorresponds to the largest whole number of prefixed symbol durationst_(CP+SYM) that is less than the 172 microsecond duration indicated bythe L-SIG field.

In an embodiment, the second station STA2 may not decode signalsreceived after the actual duration of the post-L-SIG-field portion ofthe PPDU 806.

In an embodiment, the first station STA1 may transmit no signal or anull signal during the period of the extension corresponding to thevirtual OFDM symbols 860, 862, and 864. The extension may have a zerosignal strength.

In an embodiment, the first station STA1 may transmit during the periodof the extension corresponding to the virtual OFDM symbols 860, 862, and864. The extension may have a non-zero signal strength. The signalstransmitted during the period corresponding to the virtual OFDM symbols860, 862, and 864 may be adapted to ensure proper operation of ClearChannel Assessment (CCA) process of the WLAN.

In the example shown in FIG. 8 , the extension is added to provide anadditional 12 microseconds to the available decode time t_(dec), butembodiments are not limited thereto. In an embodiment, a duration of theextension can support plural durations that are a multiple of a unit oftime. The unit of time may be 4 microseconds, and in this case theplural durations may include 0, 4, 8, 12, and 16 microseconds.

In an embodiment, the duration of the extension needs to be smaller thana 12.8 us OFDM symbol length to avoid length ambiguity of the extension.For example, as described above, if the L-SIG field indicates apost-L-SIG-field duration to the EOF that is 172 microseconds(corresponding to 43 4-microsecond virtual OFDM symbols), the secondstation STA2 may unambiguously determine that the actual duration of thepost-L-SIG-field portion of the PPDU 806 is 160 microseconds and theduration of the extension of the PPDU 806 is 12 microseconds. However,if the L-SIG field indicates a post-L-SIG-field duration to the EOF thatis 176 microseconds (corresponding to 44 4-microsecond virtual OFDMsymbols), the second station STA2 cannot unambiguously determine theactual duration of the post-L-SIG-field portion of the PPDU 806 and theduration of the extension of the PPDU 806, because the actual durationof the post-L-SIG-field portion of the PPDU 806 and the duration of theextension are not explicitly derived from L-SIG field. If a lengthindication that is not explicitly derived from the duration indicated bythe L-SIG field is sent in a High Efficiency SIG (HE-SIG) field, it ispossible to indicate more than 12 microseconds of additional availabledecode time. The HE-SIG field may include an indication for a durationof the extension to avoid length ambiguity of the extension. The lengthindication in the HE-SIG field may indicate whether the duration of theextension is greater than a predetermined duration. For example, thepredetermined duration can be 12 microseconds, when the symbol durationT_(SYM) is 12.8 microseconds and the CP duration TT_(CP) is 3.2microseconds. Because a duration of the extension can be a multiple of 4microseconds like any one of 0, 4, 8, 12, and 16 microseconds, thelength indication in the HE-SIG field can indicate TRUE if the durationof the extension is 16 microseconds, and the length indication in theHE-SIG field can indicate FALSE if the duration of the extension is anyone of 0, 4, 8, and 12 microseconds.

A first device receiving a first frame may require a different availabledecode time than a second device receiving a second frame, even whenlast frame(s) of the second frame require substantially identicalprocessing to last frame(s) of the first frame. For example, the firstdevices may require an additional 4 us of available decode time from anend of reception of a final OFDM symbol containing data that needs to bedecoded, while the second device may require an additional 12 us ofavailable decode time from the end of reception of the final OFDM symbolcontaining data that needs to be decoded.

A device may also require a different amount of additional availabledecode time according to transmission properties of the frame (that is,a transmission format of the frame.) For example, the amount ofadditional available decode time required by the device may varyaccording to one or more of the type of a Forward Error Correction (FEC)encoding (e.g., LDPC, BCC, and the like), a Modulation and Coding Scheme(MCS), a bandwidth (BW), whether STBC is used, whether SFBC is used, adata rate, and the like. Here, the MCS indicates a combination of themodulation type (like BPSK, QPSK, 16-QAM, 64-QAM, and the like) and thecoding rate (like ½, ¾, ⅔, and the like).

In an embodiment, a device may provide its capability informationincluding an indication of whether the device is capable of performingdecoding of the final symbol(s) without requiring an additional amountof available decode time according to the transmission format. Forexample, the device may provide one or more respective indications thata frame transmitted using STBC and LDPC, a frame transmitted using an 80MHz BW and LDPC, and so on may be decoded without requiring additionalavailable decoding time.

In an embodiment, a device may provide its capability informationincluding an indication of an additional amount of available decode timerequired for one or more transmission formats or for all transmissionformats.

In an embodiment, a device may provide its capability informationincluding an indication of an additional amount of available decode timerequired according to a supported MCS Capability, such as a Receive (Rx)VHC-MCS Map, an Rx Highest Supported Data Rate, and the like.

FIG. 9 illustrates a process 900 for increasing an available decode timeof a symbol encoded into a transmitted frame according to an embodiment.In an embodiment, the frame is a WLAN frame, such as, for example, aframe transmitted according to an IEEE 802.11 standard. In anembodiment, the frame is a High Efficiency PLCP Protocol Data Unit frame(HE PPDU).

The process 900 may be performed by a transmitting device, such as astation of a WLAN. In an embodiment, the transmitting device performingthe process 900 is an Access Point (AP). In an embodiment, thetransmitting device performing the process 900 is a Non-AP station.

In an embodiment, the frame is a type of frame that requires a devicereceiving the frame to transmit a response within a predetermined periodof time, the predetermined period of time being measured relative to theend of transmission of the frame. Before transmitting the response, thereceiving device may be required to decode and process all symbols inthe frame that carry information being sent to the receiving device.

In an embodiment, the predetermined period of time is a ShortInter-Frame Space (SIFS). In an embodiment, the predetermined period oftime is 16 microseconds.

At S901, the transmitting device receives capability information of areceiving device from the receiving device. The capability informationmay include a required additional processing time for one or moretransmission types. The one or more transmission types may include amodulation type, a coding rate, a bandwidth, an encoding type, whetherSTBC is used, and whether SFBC is used. The post-encoding PHY paddingbits and the extension of the frame may provide the additionalprocessing time. The capability information may include pluraladditional processing times for plural transmission formats or for allpossible transmission formats. The transmission format is a combinationof plural transmission type. For example, one transmission format mayuse a modulation type of BPSK and a bandwidth of 20 MHz, and anothertransmission format may use a modulation type of QPSK and a bandwidth of40 MHz. If five (5) modulation types and four (4) bandwidths exist, thenumber of the all possible transmission formats can be 20 (=5×4).

At 5902, the transmitting device generates a frame including an L-SIGfield, an HE-SIG field, and 12.8 us long OFDM symbols with either 0.8,1.6, or 3.2 μs cyclic prefixes (CP).

At 5903, the transmitting device determines an additional duration forthe frame, the additional duration being a duration beyond a durationused to transmit the information being sent to the receiving device. Theadditional duration may correspond to a period of time immediately afterthe transmission of a plurality of symbols that carry the informationbeing sent, using the frame, to the receiving device.

In an embodiment, the transmitting device may determine the additionalduration for the frame based on the capability information of the one ormore receiving devices. The additional duration may be determinedaccording to one or more transmission properties (that is, atransmission format) of the frame. The transmission property used todetermine the additional duration may be one or more of a bandwidth ofthe frame, a Modulation and Coding Scheme (MCS) of the frame, a type ofForward Error Correction (FEC) encoding of the frame, a data rate of theframe, whether the frame is transmitted using Space Time Block Coding(STBC), whether the frame is transmitted using Space Frequency BlockCoding (SFBC), and the like.

In an embodiment, the additional duration may be determined according toone or more characteristics of the receiving device. The one or morecharacteristics may correspond to a time required by the receivingdevice to decode and process one or more symbols of the frame.

For example, when neither STBC nor SFBC is used to transmit the frame,the one or more characteristics may correspond to a time required toprocess and decode the last symbol of the frame that include theinformation being sent to the receiving device. When one of STBC or SFBCis used to transmit the frame, the one or more characteristics maycorrespond to a time required to process and decode two of the lastsymbols of the frame that include the information being sent to thereceiving device.

At S904, the transmitting device extends the duration of the frameaccording to the additional duration. An embodiment of a process forextending the duration of the frame according to the additional durationis illustrated in FIG. 11 , described below.

In an embodiment, the transmitting device may perform the WLAN operation500 of FIG. 5 . The transmitting device may extend the duration of theframe by appending one or more Null MAC Protocol Data Units (MPDUs)(e.g., one or more End of Frame (EOF) MPDUs) to an Aggregate MPDU(A-MPDU) corresponding to the frame.

In an embodiment, the transmitting device may perform the WLAN operation600 of FIG. 6 . The transmitting device may extend the duration of theframe by appending padding bits to a data unit corresponding to theframe, and then performing a joint encoding of the data unit and thepadding bits. In an embodiment, the data unit is an MPDU or an A-MPDU.In an embodiment, the encoding is a type of Forward Error Correction(FEC) encoding, such as a Low Density Parity Check (LDPC) encoding or aBinary Convolution Code (BCC) encoding.

In an embodiment, the transmitting device may perform the WLAN operation700 of FIG. 7 . The transmitting device may extend the duration of theframe by performing an encoding of the data unit and appending paddingbits to a result of the encoding. In an embodiment, the data unit is anMPDU or an A-MPDU. In an embodiment, the encoding is a type of ForwardError Correction (FEC) encoding.

In an embodiment, the transmitting device may perform the WLAN operation800 of FIG. 8 . The transmitting device may extend the duration of theframe by indicating an extended duration in a Legacy Signal (L-SIG)field of the frame. The extended duration may be greater than theduration used to transmit the information being sent to the receivingdevice. In an embodiment, the duration indicated by the L-SIG field maybe one of 0, 4, 8 and 12 microseconds longer than the duration used totransmit the information.

At S906, the transmitting device transmits the frame.

In an embodiment, the transmitting device transmits null symbols duringthe additional duration of the frame.

In an embodiment, the transmitting device transmits signals during theadditional duration of the frame.

At S908, the transmitting device receives an Acknowledgement frame inresponse to the frame an SIFS after the end of the frame.

FIG. 10 illustrates a process 1000 of receiving and processing a framehaving an extended duration. The extended duration provides additionaltime to decode a symbol of the frame (that is, the extended durationincreases the available decoding time for the decoding of the symbol).

The process 1000 may be performed by a receiving device, such as astation of a WLAN. In an embodiment, the WLAN is a WLAN operatingaccording to an IEEE 802.11 standard.

At S1001, the receiving device determines a required additionalprocessing time. The receiving device may determine the requiredadditional processing time based on one or more transmission types. Theone or more transmission types may each include one or more of amodulation type, a coding rate, a bandwidth, and an encoding scheme.

At S1002, the receiving device provides the transmitting device withcapability information of the receiving device. The capabilityinformation may include a required additional processing time for one ormore transmission types. The post-encoding PHY padding bits and theextension of the frame may provide the additional processing time.

At S1003, the receiving device receives a frame having an L-SIG field,an HE-SIG field, 12.8 us long OFDM symbols with either 0.8, 1.6, or 3.2μs cyclic prefixes (CP), pre-encoding PHY padding bits, post-encodingPHY padding bits, and an extension for the frame. In an embodiment, theframe is an HE-PPDU frame.

At S1004, the receiving device determines a duration of a transmissionof a data unit included in the frame. In an embodiment, the data unit isan MPDU or an A-MPDU. In an embodiment, the duration of the transmissionof the data unit is relative to the end of a Legacy Signal (L-SIG) fieldof the frame.

In an embodiment, the receiving device determines the duration of thetransmission of the data unit by detecting an EOF MPDU in the data unit.

In an embodiment, the receiving device determines the duration of thetransmission of the data unit using a duration indicated in a LegacySignal (L-SIG) field of the received frame. In an embodiment, theduration of the transmission of the data unit is relative to the end ofthe L-SIG field of the frame.

In an embodiment, the transmission of the data unit is performed using aplurality of symbols, wherein each symbol has a prefixed symbolduration. The prefixed symbol duration includes a duration of the symboland a duration of a cyclic prefix associated with the symbol.

In an embodiment, the prefixed symbol duration may be any one of 13.6,14.4, and 16 microseconds.

The receiving device may determine the duration of the transmission ofthe data unit by determining a duration indicated by the L-SIG field,and determining the longest duration that is an integer multiple of theprefixed symbol duration and that is less than or equal to the durationindicated by the L-SIG field.

In an embodiment, the receiving device determines the duration of thetransmission of the data unit using a length indication of an HE-SIGfield of the received frame. The length indication indicates whether theextended duration is greater than the duration of the transmission ofthe data unit by a predetermined duration. In an embodiment, thepredetermined duration is 12 microseconds.

At S1006, the receiving device decodes a plurality of symbolscorresponding to the data unit, that is, the plurality of symbolstransmitted during the duration of the transmission of the data unit.

At S1008, the receiving device determines to transmit an Acknowledge(ACK) frame using the decoded plurality of symbols. In an embodiment,receiving device determines to transmit the ACK frame the without usinga result of decoding a symbol received after the duration of thetransmission of the data unit.

In an embodiment, the receiving device determines to transmit an ACKframe using, among other symbols, a last decoded symbol of the pluralityof symbols used to transmit the data unit, and in an embodiment,determines to transmit the ACK frame without using a result of decodingany symbol received after the last decoded symbol. As a result, theavailable decode time of the last decoded symbol may be increased.

FIG. 11 illustrates a process 1100 for extending a duration of a framein order to increase the available decode time for a symbol encoded intothe frame, according to an embodiment. The process 1100 may be performedduring S904 of the process 900 of FIG. 9 .

The process 1100 may be performed by a transmitting device that istransmitting the frame. The transmitting device may be part of a WLAN,such as a WLAN according to an IEEE 802.11 standard. The transmittingdevice may be an Access Point (AP).

FIG. 11 show some operations of the process 1100 being performed in aMedia Access Control (MAC) layer, and other operations of the process1100 being performed in a physical (PHY) layer. In an embodiment, theMAC layer corresponds to a MAC layer of an IEEE 802.11 standard and thePHY layer corresponds to the PHY layer of the IEEE 802.11 standard.

In the example shown in FIG. 11 , the frame may be a PPDU frameincluding an A-MPDU. A data portion of the PPDU frame (such as theA-MPDU) may be transmitted using symbols having a symbol duration of12.8 microseconds.

At 51104, when the process 1100 determines to perform MAC layer padding,the process 1100 proceeds to S1108. Otherwise, the process 1100 proceedsto S1110.

At S1108, the process 1100 incorporates one or more EOF MPDUs to theA-MPDU. The EOF MPDUs are appended to the end of the A-MPDU.

At S1110, when the process 1100 determines to perform bit padding in thePHY layer before performing Forward Error Correction (FEC) encoding ofthe A-MPDU, the process 1100 proceeds to S1112. Otherwise, the process1100 proceeds to S1114.

At S1112, the process 1100 appends, in the PHY layer, first padding bitsto the A-MPDU.

At S1114, the process 1100 encodes the A-MPDU using a FEC encoder toproduce a FEC encoded data unit. When the first padding bits have beenappended to the A-MPDU at S1112, the FEC encoder jointly encodes thefirst padding bits with information in the A-MPDU to produce the FECencoded data unit.

At S1116, when the process 1100 determines to perform post-FEC-encodingbit padding, the process 1100 proceeds to S1120. Otherwise, the process1100 proceeds to S1124.

At S1120, the process 1100 appends the second padding bits to the FECencoded data unit produced at S1114.

At S1124, the process 1100 determines whether the available decode timeneeds to be increased. When the available decode time needs to beincreased, the process 1100 proceeds to S1126. Otherwise, the process1100 proceeds to S1130.

At S1126, the process 1100 appends an extension to an end of the frame,and includes a length indication in an HE-SIG field of the frame. Thelength indication may indicate a duration of the extension to avoidlength ambiguity. The indication may indicate whether the duration ofthe extension is greater than 12 microseconds.

At S1130, the process 1100 sets a length field of the L-SIG field sothat the length field can indicate the end of the frame. The process1100 then ends.

In above explanations and figures, illustrative embodiments wereprovided to allow a person of skill in the art to understand andimplement embodiments of the disclosure. However, embodiments are notlimited thereto, and are therefore not limited to the number of STAs,specific identifications, specific formats, specific number of STAs peridentifications, or other specifics of the illustrative embodiments.Furthermore, while in the description and related figures the referencehas made to one or more IEEE Std 802.11 standards, embodiments are notlimited thereto, and a person of skill in the art in light of theteachings and disclosures herein would understand how the presentdisclosures apply to any wireless operation that operates in licensed orunlicensed bands.

The above explanation and figures are applied to the HE PPDU, the HE-SIGfield and the like of IEEE 802.11ax amendment, but they can also beapplied to a PPDU, an SIG field, and the like of the next amendment ofIEEE 802.11.

Embodiments of the present disclosure include electronic devicesconfigured to perform one or more of the operations described herein.However, embodiments are not limited thereto.

Embodiments of the present disclosure may further include systemsconfigured to operate using the processes described herein. The systemsmay include basic service sets (BSSs) such as the BSSs 100 of FIG. 1 ,but embodiments are not limited thereto.

Embodiments of the present disclosure may be implemented in the form ofprogram instructions executable through various computer means, such asa processor or microcontroller, and recorded in a non-transitorycomputer-readable medium. The non-transitory computer-readable mediummay include one or more of program instructions, data files, datastructures, and the like. The program instructions may be adapted toexecute the processes and to generate and decode the frames describedherein when executed on a device such as the wireless devices shown inFIG. 1 .

In an embodiment, the non-transitory computer-readable medium mayinclude a read only memory (ROM), a random access memory (RAM), or aflash memory. In an embodiment, the non-transitory computer-readablemedium may include a magnetic, optical, or magneto-optical disc such asa hard disk drive, a floppy disc, a CD-ROM, and the like.

While this invention has been described in connection with what ispresently considered to be practical embodiments, embodiments are notlimited to the disclosed embodiments, but, on the contrary, may includevarious modifications and equivalent arrangements included within thespirit and scope of the appended claims. The order of operationsdescribed in a process is illustrative and some operations may bere-ordered. Further, two or more embodiments may be combined.

What is claimed is:
 1. A wireless communication device comprising: awireless transmitter, and a processor coupled to the wirelesstransmitter, wherein the processor is configured to: generate a firstHigh Efficiency Physical Layer Protocol Data Unit (HE PPDU) including aNon-High-Throughput (Non-HT) signal (L-SIG) field, a High Efficiencysignal (HE-SIG) field, and a data field, wherein the data field includesan Orthogonal Frequency Division Multiplexing (OFDM) symbol includingpadding bits; append an extension at an end of the first HE PPDU toincrease an available processing time, the extension having a non-zerosignal strength; and transmit a second HE PPDU including the first HEPPDU and the extension, wherein the L-SIG field includes a first lengthindication of the second HE PPDU, and wherein the HE-SIG field includesa second length indication for a duration of the extension to avoidambiguity of the extension.
 2. The wireless communication device ofclaim 1, wherein the second length indication indicates whether theduration of the extension is greater than a reference duration.
 3. Thewireless communication device of claim 1, wherein the extension supportsplural durations which are a multiple of a unit of time.
 4. The wirelesscommunication device of claim 3, wherein the unit of time is 4microseconds.
 5. The wireless communication device of claim 4, whereinthe plural durations include 0, 4, 8, 12, and 16 microseconds.
 6. Thewireless communication device of claim 1, wherein the L-SIG fieldindicates an end of the extension.
 7. The wireless communication deviceof claim 6, wherein the L-SIG field includes an L-SIG length fieldindicating the end of the extension.
 8. The wireless communicationdevice of claim 1, wherein the padding bits are appended after anencoding stage encoding a MAC frame.
 9. The wireless communicationdevice of claim 1, wherein the OFDM symbol has a symbol duration of 12.8microsecond excluding a cyclic prefix.
 10. The wireless communicationdevice of claim 9, wherein the OFDM symbol supports plural cyclic prefixdurations of 0.8, 1.6, and 3.2 microseconds.
 11. A wirelesscommunication device comprising: a wireless receiver, a wirelesstransmitter, and a processor coupled to the wireless receiver and to thewireless transmitter, wherein the processor is configured to: receive afirst High Efficiency Physical Layer Protocol Data Unit (HE PPDU)including a second HE PPDU including a Non-High-Throughput (Non-HT)signal (L-SIG) field, a High Efficiency signal (HE-SIG) field, and adata field, wherein the data field includes an Orthogonal FrequencyDivision Multiplexing (OFDM) symbol including padding bits, and thefirst HE PPDU further includes an extension appended at an end of thesecond HE PPDU to increase an available processing time, the extensionhaving a non-zero signal strength; and transmit an Acknowledgement framea predetermined inter-frame space after the end of the first HE PPDU,wherein the L-SIG field includes a first length indication of the firstHE PPDU, and wherein the HE-SIG field includes a second lengthindication for a duration of the extension to avoid ambiguity of theextension.
 12. The wireless communication device of claim 11, whereinthe second length indication indicates whether the duration of theextension is greater than a reference duration.
 13. The wirelesscommunication device of claim 11, wherein the extension supports pluraldurations which are a multiple of a unit of time.
 14. The wirelesscommunication device of claim 13, wherein the unit of time is 4microseconds.
 15. The wireless communication device of claim 13, whereinthe plural durations include 0, 4, 8, 12, and 16 microseconds.
 16. Thewireless communication device of claim 11, wherein the L-SIG fieldincludes a L-SIG length field indicating an end of the extension. 17.The wireless communication device of claim 11, wherein the OFDM symbolhas a symbol duration of 12.8 microsecond excluding a cyclic prefix, andsupports plural cyclic prefix durations of 0.8, 1.6, and 3.2microseconds.
 18. The wireless communication device of claim 11, whereinthe predetermined inter-frame space is 16 microseconds.